|-38|+|45|:|-15|
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
\(=\dfrac{15}{37}\cdot\dfrac{38}{41}-\dfrac{15}{37}\cdot\dfrac{74}{45}-\dfrac{38}{41}\cdot\dfrac{15}{37}-\dfrac{38}{41}\cdot\dfrac{82}{76}\)
\(=\dfrac{-1}{3}\cdot2-\dfrac{1}{2}\cdot2=-\dfrac{2}{3}-1=-\dfrac{5}{3}\)
\(1,=38-42+14-25+27+15=27\)
\(2,=12+21-23+21-10=21\)
\(3,=57-725-605+53=-1220\)
\(4,=55+45+15-15+55-45=110\)
Đáp án B
C = 4 5 : 4 5 . - 5 4 : 16 25 - 1 5 = 4 5 : - 1 : 11 25 = 4 5 . - 1 . 25 11 = - 20 11
D = 15 8 - 15 6 - 15 32 + 15 64 3 - 3 2 - 3 4 + 3 8 = 15 1 8 - 1 6 - 1 32 + 1 64 3 . 1 - 1 2 - 1 4 + 1 8 = 15 . - 11 192 3 . 1 8 = 5 . - 11 72 = - 55 72
Vì - 55 72 > - 20 11 nên D > C
Đáp án B
C = 4 5 : 4 5 . - 5 4 : 16 25 - 1 5 = 4 5 : - 1 : 11 25 = 4 5 . - 1 . 25 11 = - 20 11
D = 15 8 - 15 6 - 15 32 + 15 64 3 - 3 2 - 3 4 + 3 8 = 15 1 8 - 1 6 - 1 32 + 1 64 3 . 1 - 1 2 - 1 4 + 1 8 = 15 . - 11 192 3 . 1 8 = 5 . - 11 72 = - 55 72
Vì - 55 72 > - 20 11 nên D > C
\(\frac{-1}{6}.\frac{-15}{19}.\frac{38}{45}=\frac{1}{9}\)
#)Giải :
\(S=\frac{38}{25}+\frac{9}{10}-\frac{11}{15}+\frac{13}{21}-\frac{15}{28}+\frac{17}{36}-\frac{19}{45}+...-\frac{119}{4950}\)
\(S=\frac{38}{25}+\left(\frac{9}{10}-\frac{11}{15}\right)+\left(\frac{13}{21}-\frac{15}{28}\right) +\left(\frac{17}{36}-\frac{19}{45}\right)+...+\left(\frac{197}{4851}-\frac{199}{4950}\right)\)
Ta thấy :
\(\left(\frac{9}{10}-\frac{11}{15}\right)=\frac{1}{6}=\frac{1}{\left(2.3\right)}=\frac{1}{2}-\frac{1}{3}\)
\(\left(\frac{13}{21}-\frac{15}{28}\right)=\frac{1}{12}=\frac{1}{\left(3.4\right)}=\frac{1}{3}-\frac{1}{4}\)
\(\left(\frac{17}{36}-\frac{19}{45}\right)=\frac{1}{20}=\frac{1}{\left(4.5\right)}=\frac{1}{4}-\frac{1}{5}\)
..........................................................
\(\left(\frac{197}{4851}-\frac{199}{4950}\right)=\frac{1}{2450}=\frac{1}{\left(49.50\right)}=\frac{1}{49}-\frac{1}{50}\)
\(\Rightarrow S=\frac{38}{25}+\left[\left(\frac{1}{2}-\frac{1}{3}\right)+\left(\frac{1}{3}-\frac{1}{4}\right)+\left(\frac{1}{4}-\frac{1}{5}\right)+...+\left(\frac{1}{49}-\frac{1}{50}\right)\right]\)
\(\Rightarrow S=\frac{38}{25}+\left[\frac{1}{2}-\frac{1}{50}\right]\)
\(\Rightarrow S=\frac{38}{25}+\frac{24}{50}\)
\(\Rightarrow S=2\)
#~Will~be~Pens~#
-7/15